PTLs 1 and 2 disclose drills in which an inner wall surface of the above cut debris discharge groove is formed by two concave circular arcs with different radii in a cross-section perpendicular to an axis. In a drill described in PTL 1 out of these drills, the radius of a circular arc formed by a cross-section of a second concave surface extending from a core diameter circle to a heel side is made greater than the radius of a circular arc formed by a cross-section of the first concave surface extending from a leading edge side to a core diameter circle. Additionally, in the drill described in PTL 2, contrary to the above, the radius of a first circle formed by a cross-section on the leading edge side in the cross-section perpendicular to the axis is made greater than the radius of a second circle on the heel side.